One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,4)(3,7,8,6)(9,10,13,16)(11,14,18,22)(12,15,20,24)(17,21,19,23)(25,26)(27,37)(28,32)(29,36)(30,35)(31,34)(33,38)(39,40)(1,3)(2,6)(4,7)(5,8)(9,11)(10,14)(12,19)(13,18)(15,23)(16,22)(17,20)(21,24)(25,27)(26,32)(28,30)(29,39)(31,38)(33,36)(34,40)(35,37) involution — undirected(9,12)(10,15)(11,17)(13,20)(14,21)(16,24)(18,19)(22,23)(25,27,30,28)(26,33,35,40)(29,38,31,39)(32,34,37,36)(3,8)(6,7)(12,20)(15,24)(17,19)(21,23)(25,28,30,27)(26,32,35,37)(29,38,31,39)(33,34,40,36)(1,4,5,2)(3,7,8,6)(10,16)(11,18)(15,24)(17,19)(25,29,30,31)(26,34,35,36)(27,38,28,39)(32,33,37,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.